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New research pushes back origin of human species by 100,000 years

Fossils found at a dig site in Morocco, described Wednesday in the journal Nature, represent "the very root of our species: the oldest Homo sapiens ever found in Africa or elsewhere.”

Views of the earliest known Homo sapiens fossils from Jebel Irhoud (Morocco) based on micro-computed scans of multiple original fossils. Dated to 300,000 years ago, these early Homo sapiens already have a modern-looking face that falls within the variation of humans living today. However, the archaic-looking virtual imprint of the braincase (blue) indicates that brain shape, and possibly brain function, evolved within the Homo sapiens lineage. (Philipp Gunz / MPI EVA Leipzig)

Researchers working in Morocco have uncovered Homo sapiens fossils that dramatically push back the origins of our species, a discovery they say should force us to rethink where, when, and how we evolved.

Thirteen years ago, a team of paleoanthropologists began excavating an old dig site known as Jebel Irhoud, a quarry midway between Marrakesh and the Atlantic Coast.

The site is unusual. In the 1960s, after miners exposed a skull, researchers excavated a braincase and a jaw that were clearly ancient but bore a confusing mishmash of features. Jebel Irhoud is also far, far away from the so-called “cradle of humanity” in East Africa. Sites in Ethiopia have gifted researchers with the oldest known fossils of Homo sapiens, generating a broad consensus that our species emerged here around 200,000 years ago.

When the team of paleoanthropologists returned to Morocco in 2004 hoping to get dates for the known fossils, they quickly discovered new ones. Altogether, there were skull fragments, teeth, and limb bones from at least five individuals: three adults, one adolescent, and one child.

3D scans and sophisticated statistical shape analyses of the skulls’ facial structure strongly suggested they were Homo sapiens, not Neanderthals or any other extinct hominin. Using a technique known as thermoluminescence, the researchers dated the site.

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The results shocked them: these humans lived approximately 300,000 years ago.

Researchers say the dates of the fossils from the excavation site in Morocco "were a big wow.” (Shannon McPherron / MPI EVA Leipzig)

“These dates were a big wow,” says Jean-Jacques Hublin of the Max Planck Institute for Evolutionary Anthropology, who led the team. The analyses “convinced us this material represents the very root of our species: the oldest Homo sapiens ever found in Africa or elsewhere.”

Jebel Irhoud — about as far away from Ethiopia as possible while still remaining on the continent — deepens our species’ African origins but challenges the idea that we evolved in one Garden-of-Eden-like crucible.

“It shows that the process was very complex,” says David Begun, a professor of anthropology at the University of Toronto who was not involved in the research. “Modern humans did not emerge from a single progressive population somewhere in Africa, but was a pan-African phenomenon.”

The fossils do not completely resolve a key question in the field: whether the full suite of modern human features evolved in a flurry, or emerged incrementally over a long period of time.

The Jebel Irhoud skulls have the weak brow ridges and shorter faces distinctive to Homo sapiens. They would not look particularly strange, at least facially, if you walked by one of them on the street, researchers say.

But they have the squat, elongated braincases associated with more primitive humans, rather than our modern globe-shaped ones. Were the Jebel Irhoud Homo sapiens one of many early Homo sapiens populations dotted around Africa that carried a few key adaptations but that were ultimately marginal to the development of our species? Or were they part of a huge gene pool spread across the whole continent, each contributing features slowly, over many hundreds of thousands of years?

Hublin believes the latter is more likely: the development of modern human biology was an accretion of adaptations, with brain size coming last. The Sahara was not always the punishing physical barrier it is today, he and others add. At times, it was greener and wetter. “During these connections there were exchanges of innovations and also exchanges of genes. Any favourable mutations would spread,” Hublin says.

Tools found at the site also support this theory, the team believes. Sharp spear points from Jebel Irhoud belong to what is known as Middle Stone Age technology. (The points are made of material not local to the area: these humans must have travelled many kilometres to make them.) Other Middle Stone Age sites with similarly ancient dates have been discovered elsewhere in Africa, suggesting that our species spread this technology as we dispersed across the continent.

But other researchers disagree, saying that linking tool technology to a particular species is misguided. It will be difficult to conclusively answer any of these questions without more fossils, a researchers have found just a handful of Homo sapiens older than 150,000 years.

This discovery will hopefully prompt others to look beyond East Africa, where so much research has been concentrated, others in the field say.

“Fossils are found where people look for them,” says Bernard Wood, university professor of human origins at George Washington University’s Center for the Advanced Study of Human Paleobiology. “The message here is that we should encourage researchers and governments that fund researchers to go and look for fossils in non-traditional places. My guess is that if you go and look, you will probably find.”

In Nature, the team also suggests that scientists should reanalyze some of the fossils we already have. Some paleoanthropologists have argued that a fragmentary skull from Florisbad in South Africa, tentatively dated to 260,000 years old and with a similar mosaic of modern and archaic features, is also an early Homo sapiens.

In another sense, the discoveries at Jebel Irhoud are predictable. Recent genetic analysis of Neanderthals and Homo sapiens has suggested that the two species split from a common ancestor roughly 500,000 to 700,000 years ago.

“We do not know the actual age of the origin of modern humans, we have just pushed it back further in time,” says Begun. “There probably are older modern human fossils in Africa waiting to be found.”

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